System and method for providing write-once-read-many (WORM) storage

ABSTRACT

Techniques for providing write-once-read-many (WORM) storage are described herein. According to one embodiment, a range of values is received to set an attribute of a file, where the received range of values is outside of an ordinary range of the attribute in accordance with a file system associated with the file. In addition, a management action is received to be associated with the received range of values of the attribute, where the management action is unrelated to an ordinary action associated with the attribute of the file in accordance with the file system. In response, the received management action is associated with the received range of values of the attribute. Other methods and apparatuses are also described.

FIELD OF THE INVENTION

The present invention relates generally to data storage. Moreparticularly, this invention relates to write-once-read-many storage.

BACKGROUND

Electronic data can be modified relatively easily and without leavingmuch of a trace. As organizations increasingly rely on electronic data,it is important to protect these data from improper modification. Oneway of protecting the data from modification is to store the data inWrite-Once-Read-Many (WORM) storage.

Many business entities rely on some form of WORM storage to storecritical data. In many industries, such as the financial services andhealthcare industries, businesses are required by strictrecords-retention regulations to archive important data, such as emails,transaction information, patient records, audit information, as well asother types of documents and data. In addition, many business entitiesplace a premium on protecting certain business records or critical datafiles from accidental or intentional alteration or deletion. WORMfunctionality such as non-erasable and non-rewritable data storage canensure long-term data permanence, even where regulatory compliance doesnot require the use of WORM storage.

Traditionally, WORM storage is implemented using optical storage wherethe storage media is inherently write-once. However, optical recordinghas not been improving at the rate of magnetic recording so that it hasbecome relatively expensive to store data in optical storage. Moreover,what is increasingly required in practice is to protect individualpieces of data (records, files, emails, data objects, etc) frommodification for some specified retention period.

Several systems that protect individual pieces of data from modificationfor some specified retention period have been introduced recently, suchas, for example, the Centera from EMC, the Data Retention 550 from IBMand the SnapLock from Network Appliance. The EMC Centera and IBM DataRetention 550 use their own non-standard interfaces to allow a user orapplication to specify that a data object should be protected fromchange for some duration. They require applications to be writtenspecifically to their own interfaces. The Network Appliance SnapLockoverloads selected attributes in standard file system interfaces to flaga file as WORM and to associate a retention period with the file. It,however, uses multiple attributes and requires multiple operations sothe act of setting the retention period and committing a file to be WORMmay not be atomic and is unnecessarily complex and costly.

SUMMARY OF THE DESCRIPTION

Techniques for providing write-once-read-many (WORM) storage aredescribed herein. According to one aspect of the invention, a range ofvalues is received to set an attribute of a file, where the receivedrange of values is outside of an ordinary range of the attribute inaccordance with a file system associated with the file. In addition, amanagement action is received to be associated with the received rangeof values of the attribute, where the management action is unrelated toan ordinary action associated with the attribute of the file inaccordance with the file system. In response, the received managementaction is associated with the received range of values of the attribute.

According to another aspect of the invention, in response to a commandto set a time attribute of a file to a first predetermined value, it isdetermined whether the first predetermined value is outside of anordinary range of values associated with the time attribute inaccordance with a file system associated with the file. If so, the fileis designated as a WORM file and a WORM retention period is configuredfor the file based on the first predetermined value.

Other features of the present invention will be apparent from theaccompanying drawings and from the detailed description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example and notlimitation in the figures of the accompanying drawings in which likereferences indicate similar elements.

FIG. 1 is a block diagram illustrating a system configuration accordingto one embodiment of the invention.

FIG. 2 is a block diagram illustrating a system for handling WORM filesaccording to one embodiment of the invention.

FIG. 3A is a data structure for storing file information according to aUNIX compatible file system.

FIG. 3B is a block diagram illustrating a data structure for storingWORM related attributes according to one embodiment.

FIG. 4 is a flow diagram illustrating a process for managing filesaccording to one embodiment of the invention.

FIG. 5 is a flow diagram illustrating a process for processing WORMfiles according to one embodiment of the invention.

FIG. 6 is a block diagram of a data processing system which may be usedwith one embodiment of the invention.

DETAILED DESCRIPTION

Techniques for providing write-once-read-many (WORM) storage aredescribed herein. In the following description, numerous details are setforth to provide a more thorough explanation of embodiments of thepresent invention. It will be apparent, however, to one skilled in theart, that embodiments of the present invention may be practiced withoutthese specific details. In other instances, well-known structures anddevices are shown in block diagram form, rather than in detail, in orderto avoid obscuring embodiments of the present invention.

Reference in the specification to “one embodiment” or “an embodiment”means that a particular feature, structure, or characteristic describedin connection with the embodiment is included in at least one embodimentof the invention. The appearances of the phrase “in one embodiment” invarious places in the specification do not necessarily all refer to thesame embodiment.

According to certain embodiments of the invention, an existing attributeassociated with a file (or record, or data object, etc) (e.g., astandard file attribute associated with a file system) can be configuredto a value outside its typical range to signal that a management actionshould be performed on the file, where the management action isunrelated to the normal operations associated with the attribute. Toreduce false signals, according to one embodiment, an acceptable rangeof values for the signal can be specified, where the acceptable range ofvalues is outside of the typical range of values of the attribute. Inone embodiment, multiple signals, each with an acceptable range ofvalues outside the typical range of values of the attribute, can bespecified for an attribute. In one embodiment, the system uses one ofthe time attributes typically associated with a file to indicate that afile should be WORM (protected from modification including delete) for aperiod of time, where the period of time is specified via the value ofthe time attribute via a file system call and/or an operating systemcall.

Examples of time attributes typically associated with a file may be amodification time (mtime), a status change time (ctime), and/or anaccess time (atime) in a typical operating system such as UNIX operatingsystem, as shown in FIG. 3A. Other systems may include other times suchas a creation time. For purposes of illustration, a term of “stime”(some time) is used to refer to any one of these time attributes.

FIG. 1 is a block diagram illustrating a system configuration accordingto one embodiment of the invention. Referring to FIG. 1, systemconfiguration 100 includes, but is not limited to, one or more clients101-102 communicatively coupled to a server 104 over a network 103 toaccess data stored in any of storage 105-107 over a network 110. Clients101-102 may be any type of clients such as a server, a personalcomputer, a “thin” client, a personal digital assistant (PDA), a Webenabled appliance, or a Web enabled cellular phone, etc. Server 104 mayinclude any type of server or cluster of servers. For example, server104 may be a storage server used for any of various different purposes,such as to provide multiple users with access to shared data and/or toback up mission critical data. Server 104 may be, for example, a fileserver (e.g., an appliance used to provide NAS capability), ablock-based storage server (e.g., used to provide SAN capability), aunified storage device (e.g., one which combines NAS and SANcapabilities), a nearline storage device, a direct attached storage(DAS) device, a tape backup device, or essentially any other type ofdata storage device. Server 104 may have a distributed architecture, orall of its components may be integrated into a single unit.

Network 103 may be any type of network such as a local area network(LAN), a wide area network (WAN) such as Internet, a corporate intranet,a metropolitan area network (MAN), a storage area network (SAN), a bus,or a combination thereof. Likewise, network 110. Storage 105-107 may be,for example, conventional magnetic disks, optical disks such as CD-ROMor DVD based storage, magnetic tape storage, magneto-optical (MO)storage media, solid state disks, flash memory based devices, or anyother type of non-volatile storage devices suitable for storing largevolumes of data. Storage 105-107 may also be combinations of suchdevices. In the case of disk storage media, the storage devices 105-107may be organized into one or more volumes of Redundant Array ofInexpensive Disks (RAID). Server 104 and/or storage 105-107 may beimplemented as part of an archive and/or backup systems such as thededuplication systems available from Data Domain, Inc. of Santa Clara,Calif.

According to one embodiment, server 104 includes a file system 108 andmanagement processing logic 109 such as WORM processing logic. Filesystem 108 may be any kind of file systems. A file system generallyrefers to a structuring of data and metadata on a storage device, suchas disks, which permits reading/writing of data on those disks and/orthe processing logic to enable such structuring. The metadata isorganized in data structures such as inodes that are used to storeinformation about a file, where the data blocks are structures used tostore the actual data for the file. The information contained in aninode, as shown in FIG. 3A, may include, for example, ownership of thefile, access permission for the file, size of the file, file type andreferences to locations on disk of the data blocks for the file. Thereferences to the locations of the file data are provided by pointers inthe inode, which may further reference indirect blocks that, in turn,reference the data blocks, depending upon the quantity of data in thefile.

Management processing logic 109 may be implemented as part of filesystem 108 or a separate module communicatively coupled to the filesystem 108. As described above, an existing attribute associated with afile (e.g., a standard file attribute associated with a file system) canbe configured to a value outside its typical range to signal that amanagement action should be performed on the file. The management actionmay be unrelated to the normal operations associated with the attribute.In one embodiment, in response to a request to set an attribute of afile to a particular value, where the attribute is a standard fileattribute of a typical file system, management processing logic 109determines whether the particular value is outside of a typical range ofvalues associated with the attribute being set in view of an ordinaryusage of the attribute. If the particular value is outside of theordinary range of values of the attribute, the management processinglogic 109 may perform certain management action or actions that havebeen previously assigned to the attribute and that may be unrelated toan ordinary action associated with the attribute in view of the filesystem. Otherwise, if the particular value is within an ordinary rangeof values associated with the attribute, the file system 108 willperform ordinary action or actions associated with the attribute.

For example, according to one embodiment, a time attribute (e.g., atime,ctime, or mtime) typically associated with a file is used to indicatethat a file should be WORM for a period of time, where the period oftime is specified via the value of the time attribute. Note thatthroughout this application, WORM related actions are used as examplesof management actions for the purpose of illustration only. It will beappreciated that other types of management actions or functions may alsobe applied.

In this example, the indication of whether a file is designated as aWORM file is unrelated to the time attribute associated with the file.When a request for setting a time attribute of a file is received, themanagement processing logic 109 determines whether the value the timeattribute is to be set to is outside of an ordinary range of the timeattribute associated with the file. If so, the management processinglogic 109 interprets this request as a request to configure the file asa WORM file and the time value to be set is related to a WORM retentiondate associated with the file being configured as a WORM file. The WORMretention date is used to determine a WORM retention period during whichthe WORM file cannot be modified or deleted. However, once the WORMretention period expires, the file can be deleted. In one embodiment,after the WORM retention period expires, the file is treated as anordinary file that can be modified or deleted. Thus, unlike aconventional method, which requires multiple operations in order toaccomplish the above purposes, a single command can be used to commit afile to be a WORM file and to configure a WORM retention period for theWORM file being committed. Other configurations may also exist.

FIG. 2 is a block diagram illustrating a system for handling WORM filesaccording to one embodiment of the invention. For example, system 200may be implemented as part of management processing logic 109 and/orfile system 108 of server 104 in FIG. 1. In this example, the managementactions are WORM related actions. Referring to FIG. 2, system 200includes, but is not limited to, an attribute decoder 202, a WORM statemanager 203, and a WORM enforcement agent 204 coupled to a systeminterface 201 and storage 205. System interface 201 may be a part offile system interface that communicates with an application via variousfile system calls dependent upon an operating system associated with thefile system. Storage 205 may be any kind of storage devices such asstorage 105-107 of FIG. 1.

According to one embodiment, a time attribute (e.g., ctime, mtime,atime) associated with a file is used to specify whether a file shouldbe committed as a WORM file and a WORM retention period for the WORMfile. In one embodiment, prior to setting a time attribute of a file todesignate the file as a WORM file, a range of values is provided tosystem 200, where the range of values is outside an ordinary range of atypical time attribute of a file in an ordinary file system. Forexample, an ordinary range of values for a time attribute such as ctime,mtime, atime is a time in the past so any future time is outside theordinary range of values for such attributes. In response, WORM relatedactions are associated with the received range of values. In thisexample, the WORM related actions are unrelated to ordinary time relatedactions.

Subsequently, when a request for setting a time attribute of a file to aspecific value is received at system interface 201 (e.g., via a filesystem call), attribute decoder 202 examines the request in view of thespecific value to determine whether the specific value is within therange of values that has been associated with WORM related actions andoutside of an ordinary range of time related values. If so, the WORMstate manager 203 is invoked to commit the file as a WORM file. In oneembodiment, the WORM state manager 203 sets a separate attribute of thefile for indicating that the file is a WORM file. In one embodiment, theordinary time attribute of the file is not modified. That is, a value tobe set to the time attribute that is outside of an ordinary range of thetime attribute is merely used to indicate that the associated file is tobe designated as a WORM file. Alternatively, the time attribute may beset to the specific value and an application can subsequently retrievethe value by pulling the file information (e.g., stat structure underUNIX operating system) via a file system call.

In addition, according to one embodiment, the value to be set is used todetermine a WORM retention period for the WORM file. The value may bestored in the system as a WORM retention date as shown in FIG. 3B, wherethe WORM retention date is used to calculate a WORM retention period forthe associated file. A WORM retention period is referred to as a timeperiod during which the associated file is designated as a WORM file.Thus, within the WORM retention period, if an application or a userattempts to modify or delete the WORM file, such an attempt will berejected by the WORM enforcement agent 204 and/or an error message(e.g., a permission denied error) may be presented to the application oruser, indicating that the file is a WORM file and cannot be modified ordeleted. However, when the WORM retention period of the file expires,the file may be deleted. In one embodiment, after the WORM retentionperiod expires, the file is treated as an ordinary file that can bemodified or deleted.

Therefore, a single command may be used to commit a file as a WORM fileand configure the WORM retention period for the WORM file. For example,according to one embodiment, a single command may be implemented as acommand touch as follows:

-   -   touch -a -t [time] [filename]        where the [time] is the value to be set as a WORM retention        date.

According to one embodiment, a minimum WORM retention period (alsoreferred to as a minimum WORM retention time) and a maximum WORMretention period (also referred to as a maximum WORM retention time) maybe specified on a per file system or subsystem (e.g., disk/tape, volume,directory) basis. A WORM retention period of a file may be determinedbased on the value to be set as a WORM retention date of the file inview of the minimum WORM retention period and the maximum WORM retentionperiod associated with the file system/subsystem in which the file isstored.

For example, according to one embodiment, if system 200 receives arequest to set the “stime” to a value beyond a current time (e.g.,current system time associated with the file system) plus the maximumWORM retention period, the system rejects the request and returns apermission denied error. If the system receives a request to set the“stime” to a value below the current time plus the minimum WORMretention period, the system may ignore the request.

In many operating and/or file systems, setting of the “stime” can beaccomplished with the command touch set forth above. Setting of “stime”can also be accomplished programmatically through standard operatingsystem calls, which may be mapped to standard network file interfaces(e.g. NFS, CIFS). In addition, the system may further enforce regularaccess controls in addition to the WORM protection. In other words, thesystem may allow a file to be modified only if the user attempting themodification has a permission to modify the file and the file is not aWORM file.

In one embodiment, the system may allow the permission or access controlinformation of a WORM file to be updated. For example, the system mayallow the permission or access control of a WORM file to be updated toprevent certain users from reading the file. In one embodiment, when thesystem receives a request to set the “stime” of a WORM file to a valuelarger than the current WORM retention date but less than the currenttime plus the maximum WORM retention period, the system extends the WORMretention date of the file to the requested value of “stime”. In oneembodiment, when the system receives a request to set the “stime” of aWORM file to a value smaller than the current WORM retention date, thesystem may reject the request with a permission denied error. This maybe used to serve as a test for whether a file is a WORM file. In oneembodiment, the WORM retention date of a WORM file is stored as its“stime” value and can be displayed by the command such as

-   -   1s-1--time=stime [filename]        Other configurations may also exist. Note that some or all of        the components as shown in FIG. 2 may be implemented in        software, hardware, or a combination of both.

FIG. 4 is a flow diagram illustrating a process for managing filesaccording to one embodiment of the invention. Note that process 400 maybe performed by processing logic which may include software, hardware,or a combination thereof. For example, process 400 may be performed bysystem 200 of FIG. 2. Referring to FIG. 4, at block 401, processinglogic receives a range of values to be associated with an attribute of afile, such as, for example, atime, ctime, and/or mtime in accordancewith a file system, and a management action. In one embodiment, thereceived range of values is outside of an ordinary range of values ofthe attribute (e.g., time range associated with a time attribute). Inone embodiment, the management action is unrelated to an ordinary action(e.g. read/write the time attribute) associated with the attribute. Atblock 402, processing logic associates the management action (e.g., WORMrelated action) with the received range of values for the attribute.

Subsequently, at block 403, when a request is received to set theattribute of the file to a particular value, at block 404, processinglogic determines whether the particular value is within the previouslyconfigured range of values (e.g., during blocks 401-402) for theattribute. If so, at block 405, processing logic performs the managementaction (e.g., WORM related action) associated with the attribute. In oneembodiment, processing logic performs the management action associatedwith the attribute without performing the ordinary action (e.g., settinga time value to a time attribute) associated with the attribute. Thus,an existing attribute of a file in accordance with a file systemassociated with the file can be used for a management purpose other thanan ordinary file system function associated with the attribute.Furthermore, a specific value may also be used to indicate a specifickind of management action to be performed.

FIG. 5 is a flow diagram illustrating a process for processing WORMfiles according to one embodiment. Note that process 500 may beperformed by processing logic which may include software, hardware, or acombination thereof. For example, process 500 may be performed by system200 of FIG. 2. Referring to FIG. 5, at block 501, processing logicreceives and configures a minimum WORM retention period/time and amaximum WORM retention period/time to be associated with a file systemor a subsystem (e.g., disk/tape, volume, or directory, etc.) At block502, processing logic receives and stores a file in the filesystem/subsystem. Subsequently, at block 503, processing logic receivesa command to set a time attribute of the file to a predetermined value.

In response to the command, at block 504, processing logic determineswhether the predetermined value is greater than a current time plus theminimum WORM retention period and less than the current time plus themaximum WORM retention period. Note that greater than and less than mayinclude equality. Note also that the current time may be derived from asystem time associated with the file system or storage system/subsystem.If so, at block 505, processing logic designates or commits the file asa WORM file and sets the WORM retention date for the file based on thepredetermined value similar to one as shown in FIG. 3B; otherwise, thecommand is rejected. In one embodiment, if the predetermined value isless than a current time plus the minimum WORM retention period, thecommand is ignored. Referring to FIG. 3B, the predetermined value maybe, for example, “072510”, to indicate that the WORM retention date isJul. 25, 2010 for the purposes of illustration. As can be seen, such avalue, being in the future, is outside of an ordinary range of valuesassociated with a time attribute of a file in accordance with anordinary file system.

Thereafter, referring back to FIG. 5, in response to a request to modifyor delete the file, at block 506, processing logic determines whetherthe file is still designated as a WORM file and if so, whether the fileis still within its WORM retention period for example, by examining acurrent time in view of the WORM retention date associated with thefile. If so, at block 507, the request is rejected. In one embodiment,after the WORM retention period expires, the file is treated as anordinary file that can be modified or deleted. In one embodiment, afterthe WORM retention period expires, the file may only be deleted.

FIG. 6 is a block diagram of a data processing system which may be usedwith one embodiment of the invention. For example, the system 600 shownin FIG. 6 may be used as a client computer system such as clients101-102 of FIG. 1. Alternatively, the exemplary system 600 may beimplemented as a server 104 of FIG. 1.

Note that while FIG. 6 illustrates various components of a computersystem, it is not intended to represent any particular architecture ormanner of interconnecting the components; as such details are notgermane to the present invention. It will also be appreciated thatnetwork computers, handheld computers, cell phones, and other dataprocessing systems which have fewer components or perhaps morecomponents may also be used with the present invention. The computersystem of FIG. 6 may, for example, be an Apple Macintosh computer or anIBM compatible PC.

As shown in FIG. 6, the computer system 600, which is in a form of adata processing system, includes a bus or interconnect 602 coupled to aprocessor 603 and a ROM 607, a volatile RAM 605, and a non-volatilememory 606. Processor 603 may include multiple processors and/or corelogics that constitute central processing units (CPUs) of the system andthus, control the overall operations of the system. According to certainembodiments, processor 603 accomplish this by executing software storedin any of the memories 605-607, such as, for example, applications andoperating system, etc. Processor 603 may include, one or moreprogrammable general-purpose or special-purpose microprocessors, digitalsignal processors (DSPs), programmable controllers, application specificintegrated circuits (ASICs), programmable logic devices (PLDs), or thelike, or a combination of such devices.

The processor 603, which may be, for example, an Intel processor or aPowerPC processor, is coupled to cache memory 604 as shown in theexample of FIG. 6. The bus 602 interconnects these various componentstogether and also interconnects these components 603 and 605-607 to adisplay controller and display device 608, as well as to input/output(I/O) devices 610, which may be mice, keyboards, modems, networkinterfaces, printers, and other devices which are well-known in the art.

Typically, the input/output devices 610 are coupled to the systemthrough input/output controllers 609. The volatile RAM 605 is typicallyimplemented as dynamic RAM (DRAM) which requires power continuously inorder to refresh or maintain the data in the memory. The non-volatilememory 606 is typically a magnetic hard drive, a magnetic optical drive,an optical drive, a DVD RAM, a Flash memory, or other type of memorysystem which maintains data even after power is removed from the system.Typically, the non-volatile memory will also be a random access memory,although this is not required.

While FIG. 6 shows that the non-volatile memory is a local devicecoupled directly to the rest of the components in the data processingsystem, it will be appreciated that the present invention may utilize anon-volatile memory which is remote from the system, such as a networkstorage device which is coupled to the data processing system through anetwork interface such as a modem or Ethernet interface. The bus 602 mayinclude one or more buses connected to each other through variousbridges, controllers, and/or adapters, as is well-known in the art. Inone embodiment, the I/O controller 609 includes a USB (Universal SerialBus) adapter for controlling USB peripherals. Alternatively, I/Ocontroller 609 may include an IEEE-1394 adapter, also known as FireWireadapter, for controlling FireWire devices. Other components may also beincluded.

Thus, techniques for providing write-once-read-many (WORM) storage havebeen described herein. Some portions of the preceding detaileddescriptions have been presented in terms of algorithms and symbolicrepresentations of operations on data bits within a computer memory.These algorithmic descriptions and representations are the ways used bythose skilled in the data processing arts to most effectively convey thesubstance of their work to others skilled in the art. An algorithm ishere, and generally, conceived to be a self-consistent sequence ofoperations leading to a desired result. The operations are thoserequiring physical manipulations of physical quantities. Usually, thoughnot necessarily, these quantities take the form of electrical ormagnetic signals capable of being stored, transferred, combined,compared, and otherwise manipulated. It has proven convenient at times,principally for reasons of common usage, to refer to these signals asbits, values, elements, symbols, characters, terms, numbers, or thelike.

It should be borne in mind, however, that all of these and similar termsare to be associated with the appropriate physical quantities and aremerely convenient labels applied to these quantities. Unlessspecifically stated otherwise as apparent from the above discussion, itis appreciated that throughout the description, discussions utilizingterms such as “processing” or “computing” or “calculating” or“determining” or “displaying” or the like, refer to the action andprocesses of a computer system, or similar electronic computing device,that manipulates and transforms data represented as physical(electronic) quantities within the computer system's registers andmemories into other data similarly represented as physical quantitieswithin the computer system memories or registers or other suchinformation storage, transmission or display devices.

Embodiments of the present invention also relate to an apparatus forperforming the operations herein. This apparatus may be speciallyconstructed for the required purposes, or it may comprise ageneral-purpose computer selectively activated or reconfigured by acomputer program stored in the computer. Such a computer program may bestored in a computer readable storage medium, such as, but is notlimited to, any type of disk including floppy disks, optical disks,CD-ROMs, and magnetic-optical disks, read-only memories (ROMs), randomaccess memories (RAMs), erasable programmable ROMs (EPROMs),electrically erasable programmable ROMs (EEPROMs), magnetic or opticalcards, or any type of media suitable for storing electronicinstructions, and each coupled to a computer system bus.

The algorithms and displays presented herein are not inherently relatedto any particular computer or other apparatus. Various general-purposesystems may be used with programs in accordance with the teachingsherein, or it may prove convenient to construct more specializedapparatus to perform the required method operations. The requiredstructure for a variety of these systems will appear from thedescription below. In addition, embodiments of the present invention arenot described with reference to any particular programming language. Itwill be appreciated that a variety of programming languages may be usedto implement the teachings of embodiments of the invention as describedherein.

A machine-readable medium may include any mechanism for storing ortransmitting information in a form readable by a machine (e.g., acomputer). For example, a machine-readable medium includes read onlymemory (“ROM”); random access memory (“RAM”); magnetic disk storagemedia; optical storage media; flash memory devices; electrical, optical,acoustical or other form of propagated signals (e.g., carrier waves,infrared signals, digital signals, etc.); etc.

In the foregoing specification, embodiments of the invention have beendescribed with reference to specific exemplary embodiments thereof. Itwill be evident that various modifications may be made thereto withoutdeparting from the broader spirit and scope of the invention as setforth in the following claims. The specification and drawings are,accordingly, to be regarded in an illustrative sense rather than arestrictive sense.

1. A computer-implemented method for managing files, comprising:associating a range of values with a time attribute of a file, whereinthe range of values is outside of an ordinary range of the timeattribute in accordance with a file system associated with the file,wherein the time attribute is a standard file attribute of the filesystem; associating a management action with the range of values of thetime attribute, wherein the management action includes an action that isunrelated to an ordinary action associated with the time attribute ofthe file in accordance with the file system, where in the ordinaryaction includes setting a time value of the time attribute; in responseto a request subsequently received from a client via a standard call ofthe file system to set the time attribute of the file to a predeterminedvalue, determining whether the predetermined value is within the rangeof values and is outside of the ordinary range of the time attribute ofthe file; and performing the management action if the predeterminedvalue is within the range of values and is outside of the ordinary rangeof the attribute of the file, including designating the file as awrite-once-read-many (WORM) file, and setting a WORM retention period ofthe WORM file based on the predetermined value, wherein the designatingthe file and setting the WORM retention period are performed in responseto the request as a single request from the client.
 2. The method ofclaim 1, wherein the time attribute of the file is defined in a standardmetadata data structure associated with the file.
 3. The method of claim2, further comprising performing the ordinary action associated with thetime attribute of the file if the predetermined value is within theordinary range of the time attribute in accordance with a file systemassociated with the file.
 4. The method of claim 2, wherein the timeattribute of the file is not modified if the predetermined value iswithin the range of values.
 5. The method of claim 2, further comprisingperforming the ordinary action associated with the time attribute of thefile in addition to the management action.
 6. The method of claim 2,wherein the range of values includes a minimum time and a maximum time.7. The method of claim 6, further comprising setting a separateattribute associated with the file to indicate that the file is a WORMfile without modifying the time time attribute of the file.
 8. Themethod of claim 6, wherein the time attribute of the file is one of anaccess time (atime) attribute, a status change time (ctime) attribute,and a modified time (mtime) attribute compatible with the file systemassociated with the file.
 9. The method of claim 6, wherein determiningwhether the predetermined value is within the range of values and isoutside of the ordinary range of the time attribute of the filecomprises determining whether the predetermined value is greater than acurrent time plus the minimum time and less than the current time plusthe maximum time, wherein the file is designated as the WORM file andthe WORM retention period for the file is set based on the predeterminedvalue if the predetermined value is greater than the current time plusthe minimum time and less than the current time plus the maximum time.10. The method of claim 9, wherein setting the WORM retention periodcomprises storing the predetermined value as a WORM retention date in aseparate attribute for the file.
 11. The method of claim 9, furthercomprising: in response to a request for modifying the file, determiningwhether the file is designated as a WORM file; and rejecting the requestif the file is designated as a WORM file.
 12. The method of claim 11,wherein determining whether the file is designated as a WORM filecomprises: determining a WORM retention date of the file based on theWORM retention period, and comparing the current time with the WORMretention date of the file, wherein the file is a WORM file if thecurrent time is less than the WORM retention date of the file.
 13. Themethod of claim 9, further comprising: in response to a second requestto set the time attribute of the file to a second predetermined value,determining a WORM retention date of the file based on the WORMretention period, determining whether the second predetermined value isgreater than the WORM retention date of the file and less than thecurrent time plus the maximum time; and updating the WORM retention dateto the second predetermined value if the second predetermined value isgreater than the WORM retention date of the file and less than thecurrent time plus the maximum time.
 14. A system for managing files,comprising: a processor; and a memory for storing instructions, whichwhen executed from the memory, cause the processor to associate a rangeof values with a time attribute of a file, wherein the range of valuesis outside of an ordinary range of the time attribute in accordance witha file system associated with the file, wherein the time attribute ofthe file is a standard file attribute of the file system, associate amanagement action with the range of values of the time attribute,wherein the management action includes an action that is unrelated to anordinary action associated with the time attribute of the file inaccordance with the file system, where in the ordinary action includessetting a time value of the time attribute; in response to a requestsubsequently received from a client via a standard call of the filesystem to set the time attribute of the file to a predetermined value,determine whether the predetermined value is within the range of valuesand is outside of the ordinary range of the time attribute of the file,and perform the management action if the predetermined value is withinthe range of values and outside of the ordinary range of the timeattribute of the file, including designating the file as awrite-once-read-many (WORM) file, and setting a WORM retention period ofthe WORM file based on the predetermined value, wherein the designatingthe file and setting the WORM retention period are performed in responseto the request as a single request from the client.
 15. Amachine-readable storage medium having instructions stored therein,which when executed by a processor, cause the processor to perform amethod for managing files, the method comprising: associating a range ofvalues with a time attribute of a file, wherein the range of values isoutside of an ordinary range of the time attribute in accordance with afile system associated with the file, wherein the time attribute of thefile is a standard file attribute of the file system, associating amanagement action with the range of values of the time attribute,wherein the management action includes an action that is unrelated to anordinary action associated with the time attribute of the file inaccordance with the file system, in response to a request subsequentlyreceived from a client via a standard call of the file system to set thetime attribute of the file to a predetermined value, determining whetherthe predetermined value is within the range of values and is outside ofthe ordinary range of the time attribute of the file, and performing themanagement action if the predetermined value is within the range ofvalues and outside of the ordinary range of the time attribute of thefile, including designating the file as a write-once-read-many (WORM)file, and setting a WORM retention period of the WORM file based on thepredetermined value, wherein the designating the file and setting theWORM retention period are performed in response to the request as asingle request from the client.
 16. A machine-readable storage mediumhaving instructions stored therein, which when executed by a processor,cause the processor to perform a method for managing files, the methodcomprising: associating a range of values with a time attribute of afile, wherein the range of values is outside of an ordinary range of thetime attribute in accordance with a file system associated with thefile, wherein the time attribute of the file is a standard fileattribute of the file system, associating a management action with therange of values of the time attribute, wherein the management actionincludes an action that is unrelated to an ordinary action associatedwith the time attribute of the file in accordance with the file system,where in the ordinary action includes setting a time value of the timeattribute; in response to a request subsequently received from a clientvia a standard call of the file system to set the time attribute of thefile to a predetermined value, determining whether the predeterminedvalue is within the range of values and is outside of the ordinary rangeof the time attribute of the file, and performing the management actionif the predetermined value is within the range of values and outside ofthe ordinary range of the time attribute of the file, includingdesignating the file as a write-once-read-many (WORM) file, and settinga WORM retention period of the WORM file based on the predeterminedvalue, wherein the designating the file and setting the WORM retentionperiod are performed in response to the request as a single request fromthe client.
 17. The method of claim 16, further comprising: storing thefirst predetermined value as a WORM retention date in a separateattribute of the file if the first predetermined value is greater thanthe current time plus the minimum WORM retention time and less than thecurrent time plus the maximum WORM retention time.
 18. The method ofclaim 17, further comprising: in response to a second request to set thetime attribute of the file to a second predetermined value, determiningthe WORM retention date of the file based on the WORM retention period,determining whether the second predetermined value is greater than theWORM retention date and less than the current time plus the maximum WORMretention time; and updating the WORM retention date to the secondpredetermined value if the second predetermined value is greater thanthe WORM retention date and less than the current time plus the maximumWORM retention time.